In the field of photomechanical processes, there has been a need for photographic light-sensitive materials which are excellent in original reproducibility, and which are suitable for stable processing solutions or simplied replenishment methods, to cope with the diversification and complexty of printed matters.
In particular, line originals to be subjected to the process of picture taking normally comprise photo-composed letters, handwritten letters, illustrations, dot photographs, etc. Thus, line originals are normally formed of a mixture of images having different densities and line widths. Therefore, there has been a need for plate-making cameras, photographic light-sensitive materials, and image formation methods which give excellent reproduction of these originals.
On the other hand, enlargement or reduction of dot photograph is widely performed to make plates for catalogues or large-sized posters. In the dot enlargement process, the number of lines per inch area is reduced, giving an unsharp picture. In the dot reduction process, the number of lines per inch is increased, giving a fine picture. Accordingly, an image formation method has been desired which provides a wider latitude to maintain excellent reproducibility of dot gradation.
The light source for plate-making cameras is a halogen or xenon lamp. In order to be sufficiently sensitive to these light sources, light-sensitive materials are normally subjected to orthochromatic sensitization. However, it has been found that the photographic light-sensitive materials thus orthochromatically sensitized are more susceptible to the effects of chromatic aberration of the lens which can deteriorate picture quality, particularly when a xenon lamp is used.
In a known method for meeting the demand for wide a latitude, a lithographic silver halide photographic material comprising silver bromochloride (at least having a silver chloride content of 50% or more) is processed with a hydroquinone developer having an extremely low effective concentration of sulfurous ions (normally 0.1 mol/l or less) so that one can obtain line originals or dot images having a high contrast and a blackened density in which the image portion and the nonimage portion are clearly distinguishabl from each other. However, this method is disadvantageous in that the development is extremely unstable to air oxidation due to the low sulfurous acid concentration of the developer. In order to stabilize the activity of the developer, various efforts and measures must be made. Furthermore, this method provides a remarkably low processing speed, lowering the working efficiency.
Thus, an image formation method has been desired which comprises development with a processing solution having an excellent storage stability to provide ultrahigh contrast while eliminating the instability in the formation of images associated with the above mentioned development method (i.e., a lithographic development system). In the systems as proposed in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606, and 4,311,781, a surface latent image type silver halide photographic material comprising a specific acylhydrazine compound is processed with a developer having a pH value of 11.0 to 12.3, containing 0.15 mol/l or more of a sulfurous acid preservative, and having an excellent storage stability, to form an ultrahigh contrast negative image having .gamma. of more than 10. This new image formation system is characterized in that it can use silver bromoiodide and silver bromochloroiodide while the prior art ultrahigh contrast image formation systems can use only silver bromochloride having a high silver chloride content.
The above-mentioned image formation system is excellent in dot sharpness, processing stability and rapidity, and original reproducibility. In order to cope with the recent diversification of printed matters, a system has been desired which provides greater stability and higher original reproducibility.
A light-sensitive material comprising a redox compound which undergoes oxidation to release a photographically useful group is disclosed in JP-A-61-213847 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"), 62-260153, 64-88451 and 64-72140, and U.S. Pat. No. 4,684,604. However, in an ultrahigh contrast processing system using a hydrazine derivative, these redox compounds need to be used in large amounts to provide excellent line original and dot image reproducibility. Since an inhibitor which has been released upon development partially effuses, it will gradually accumulate in the developer as a large amount of a light-sensitive material containing these redox compounds is processed. Accordingly, when development is effected with such a fatigued developer, an ultrahigh contrast can hardly be provided or a reduced sensitivity results. In particular, if an automatic developing machine is also used for light-sensitive materials for picture taking, contact light-sensitive materials, scanner light-sensitive materials or photographic light-sensitive materials as well as light-sensitive materials containing these redox compounds, photographically adverse effects will occur on these light-sensitive materials.
Therefore, the amount of these redox compounds to be used is limited, making it impossible to accomplish satisfactory results. Furthermore, such a system can be applied to a closed system in which a light-sensitive material and a developer are restricted within a narrow range. Thus, the known systems leave much to be desired.